Sliders are known, for example, from DE-AS 17 80 488, EP 0 503 954 A1, or DE 199 44 684 C1.
Moreover, a slider is known from WO 02/070328 A1, which has two guide rails with toothed strips, on which a slide is mounted and able to move, which carries a fifth wheel. A locking mechanism with clamping shoes, engaging with toothed strips, is arranged on the slide.
The sliders which have become known thus far are designed to make an adjustment in regard to the distance between tractor and trailer before the drive begins. However, it has been found that the gap or intermediate space arising between the front of the trailer and the cabin of the tractor results in aerodynamic vortices during the drive, which influence the air drag and thus the fuel consumption of the rig.
In order to counteract this effect, wind deflectors are often mounted on the cabin of the tractor, in order to guide the air deliberately across the gap. Furthermore, it is quite sensible to make the gap or intermediate space as small as possible. On the other hand, a gap adjusted to be too small will result, on curves or due to interactions of the payload when braking the rig, to the front of the trailer or its edges knocking against the driver's cabin.
Situations can also occur in which it is advisable to allow a large gap, for example, in order to make room for equipment or to improve access to the utility lines and their connections when the vehicle is parked.
With the known sliders, although a changing of the gap between tractor and trailer is possible, still the driver must open the mechanics of the slider, then change the size of the gap by moving the tractor, lock the mechanics once more and make sure of its properly locked status. The movement of the fifth wheel and thus the trailer relative to the tractor can also be assisted by means of a motor-operated drive unit. This process requires some skill and can result in serious bodily strain for the drivers. Furthermore, this is only possible when the vehicle is parked, never during the drive.